"Space Pirate encrypted data decoded."

The subject of this article is not named in-game.
The current title is from the game's internal data.

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"The Fission Metroid is a mutant, capable of splitting in two."

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Bigbug01 and Bigbug02 are the internal file names for two creatures in Metroid: Samus Returns.


These large creatures appear in the sidescrolling backgrounds of Area 2, Area 5 and Area 6 on SR388, but are never directly encountered by Samus Aran. This may suggest that they are not hostile creatures, unlike most of the others on the alien planet. They are original to Samus Returns and did not exist in Metroid II: Return of Samus, as the backgrounds in the latter are mostly black, with a few minor exceptions.

Samus is unable to physically interact with either of the Bigbugs, which are exclusively located in the backgrounds, and none of her weapons can harm them, including the Power Bomb. Despite their large bodies and sluggish speed, they seem to have somehow managed to avoid predation by Metroids.


Bigbug01 is located in the first desert-themed room of Area 6 outside the caves with purple liquid. It appears to be a massive, slug-like creature, with several large spikes on its head and smaller one down its backside. It also has a single yellow eye. The creature slides slowly through the background and eventually disappears behind the rock walls.


Bigbug02 is a large, six-eyed species that resides near water in Area 2 and Area 5. It has a long red neck, appendages that look like whiskers and two light-purple legs or wings standing in a hunched-over, bipedal position.

It is seen in multiple rooms on the western side of Area 2. In the first room, a long shaft with a waterfall, it is seen drinking from the water; although it will leave when it spots Samus the first time she goes through the area, it will return and drink from the water and will no longer be bothered by her presence, indicating it has become tolerant of her presence. In the next room (near the Alpha's chamber), it can be seen near steam vents, doing nothing. In a third room, two Bigbug02 specimens can be seen lying in profile in the background, once again doing nothing.

Another Bigbug02 appears in a fourth room in Area 5 (near a water-filled room in the area's middle level), where it can be seen entering the water in the background.


  • While neither Bigbug appears notably insectoid, "bug" seems to be the internal naming scheme for background creatures in Samus Returns, as seen with the Bugfly, Bugcrystal, and Bug05.


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